This invention relates generally to fluid control valves and particularly to fluid control valves of the throttling type.
Throttling type fluid control valves are characterized by an ability to precisely control flow through flow openings or ports which are generally adjustable in size. Such valves may be suitable for high pressure or low pressure use or for use with caustic fluids, gases, etc. The present invention is directed to a rotary disc throttling control valve which exhibits precise flow control, is suitable for use in high pressure flowpaths, exhibits high operating efficiency, that is, does not substantially impede fluid flow when in the open or "on" position and does not leak when in the closed or "off" position.
The throttling control valve of the present invention is of the movable disc type and includes a single, flat, highly polished, ported rotatable disc positioned between fixed end retainers having corresponding ports. Rotation of the disc relative to the end retainers varies the areas of the ports in the flowpath and thus controls fluid flow. There are different types of throttling disc valves in the prior art. Many are unsuitable for use in high pressure flow lines. Those that are useful with high pressure, generally have a disc operating mechanism situated in the downstream side of the flowpath to vary the size of the port openings and hence to control fluid flow. Such mechanisms are necessarily of heavy construction to withstand the high pressures. One prior art valve includes a stationary disc and a movable disc that is operated by a rotational fork that engages the periphery of the movable disc. The movable disc is on the upstream side of the flowpath. In one version the flowpath turns just downstream of the fork so that the operating mechanism for the fork is not in the flowpath. In another version, an operating handle protrudes from the side of the valve body to permit the operating mechanism to be out of the flowpath. The valves in both versions appear to be massive, quite complicated to manufacture and assemble and quite expensive
Most prior art rotary disc type throttling valves for high pressure applications are also unidirectional, usually having a stationary disc with a movable disc mounted to the axis thereof. Most use flowpath pressure to help provide a seal and are so constructed as to not be suitable for use in bidirectional flowpaths. They also generally appear to be of very expensive construction.
In a copending application of H. Walton and S. Kehoe, Ser. No. 06/443,704, filed Nov. 22, 1982, entitled "Bidirectional Disc Throttling Valve" and assigned to the present assignee, a pair of machined, relatively adjustable, throttling discs with corresponding ports are supported for both rotational and lateral movement in bearing races in a pair of end retaining rings situated at opposite ends of the flowpath. A toggle link arrangement is used for moving the two discs in opposite angular directions, responsive to vertical movement of an operating stem or rod. A number of seals are provided, which cooperate with the pressure flow to provide a seal between the movable discs and the end retaining ring, depending upon the direction of flow in the flowpath. While the arrangement is generally satisfactory in serving its intended purpose, occasionally high breakout forces are required to move the downstream disc in its bearing race. In some environments this requires the provision of more expensive operating mechanisms. Also, the downstream disc is peripherally supported by the end retaining ring and can experience a greater degree of flexure than the upstream disc which can lead to wear and leakage.